This invention relates to bicycles. In particular the invention relates to a crank arm and chainring carrier assembly.
The crankset is the component of a bicycle drivetrain that converts the pedaling motion of the rider's legs into rotational motion used to drive a chain or belt, which in turn drives a rear wheel of the bicycle. The crankset typically carries one or more chainrings or chainwheels attached to one of the two crank arms of the crankset—commonly the right-side crank arm—either directly or through a chainring carrier. The crankset is connected to the rider by pedals attached to the crank arms, to the bicycle frame by a bottom bracket and axle, and to a rear sprocket, cassette or freewheel via the chain.
The chainring or chainrings are typically attached to the right-side crank arm of the crankset and supported by a chainring carrier. In one such example, the chainring carrier may be separate from the drive-side crank arm. Other chainring carriers are integral to the drive-side crank arm. Separate, detachable chainring carriers enable a wide variety of chainring patterns to be used with the same crank arm.
A category of power meters are used on bicycles by integration into a chainring carrier, such as those designed and manufactured by Quarq®. The chainring carrier power meter includes strain gages and electronics to measure the torque applied thereto and when combined with angular velocity, power can be calculated. Chainring carrier-based power meters are typically assembled to a crank arm in the same fashion as non-power meter chainring carriers, via a press or interference fit. While connection of these chainring carriers to the crank arm is largely via the press fit of chainring carrier to crank arm via interconnected splines or the like, the connection may be supplemented by screws, although the screws do not function to any significant extent in transmitting torque from one part to another. These press fit connections convey most or all of the torque from the crank arms to the chainring carrier through the splined connection of crank arm and chainring carrier.
When attaching a chainring carrier to a crank arm the connection between the chainring carrier and crank arm should provide for quick and simple installation and result in a reliable connection. When the chainring carrier includes power meter elements, the connection should also take into consideration the transfer of torque from the crank arms to the chainring carrier such that accurate torque measurements can be made by the power meter.
There is a demand, therefore, to provide a bicycle with an effective crank arm and chainring carrier assembly. The invention satisfies the demand.